1. Field of the Invention
The present invention relates to an electronic circuit and a method for protecting electronic devices, in particular for protecting the enabling of chip functions.
Certain forms of electronic circuits, for example chip cards, require a high degree of secrecy of the information or stored data contained in the circuit (for example keys in encryption technology). This information which relates to safety must be protected both against analyses by third parties and against manipulation. It is necessary in particular to avoid unauthorized persons acquiring access to the information by repeating unauthorized access attempts to the respective electronic device with such frequency that analysis of the security-related information or access is made possible. This may be the case, for example, if a PIN is discovered through repeated trials. A chip or chip card is therefore protected in such a way that after a certain number of unauthorized access attempts any further access attempt, and therefore as a rule even an authorized access, is prohibited. The security measures are then in certain circumstances too rigid because, for example, even the person with access authorization is no longer allowed access after, for example, only two inadvertent failed attempts. It is also possible for such an event to occur in the case of a defect in the terminal, which leads to the access authorization not being correctly detected by the terminal.